class_docstr: Widget displaying an editable color gradient. The user may add, move, recolor,
  or remove colors from the gradient. Additionally, a context menu allows the 
  user to select from pre-defined gradients.
code: def widgetGroupInterface(self):
      return (
          self.sigGradientChanged,
          self.saveState,
          self.restoreState,
      )
  
file_path: pyqtgraph/pyqtgraph/widgets/GradientWidget.py
imports: from ..graphicsItems.GradientEditorItem import GradientEditorItem
  from ..Qt import QtCore, QtGui, QtWidgets
  from .GraphicsView import GraphicsView
label_desc: Use image node_id 5 for calling the GradientWidget obj's underlying member method code with example usage: obj.widgetGroupInterface() and returns: self,  self,  self